Table 4.5b

Committed Equivalent Dose per Unit Activity of 222Rn Ingested (Sv Bq-1) for Various Subjects (Base Case Assumption Regarding Diffusion of Radon into the Stomach Wall)

 

Age at Intake (yr)

Organ

Infant

1-yr

5-yr

10-yr

15-yr

Adults

Adrenals

2.5E-09

1.0E-09

5.1E-10

3.0E-10

2.3E-10

2.0E-10

Bladder

6.3E-10

4.6E-10

2.6E-10

1.4E-10

1.1E-10

9.9E-11

Endosteal Tissue

1.5E-08

1.1E-08

5.0E-09

3.3E-09

2,7E-09

1.8E-09

Brain

1.2E-09

9.9E-10

5.0E-10

2.9E-10

2.2E-10

2.0E-10

Breast

5.9E-10

4.3E-10

2.4E-10

1.3E-10

9.7E-11

8.5E-11

Stomach Wall

3.0E-07

1.6E-07

7.3E-08

4.2E-08

3.1E-08

2.4E-08

Small Intestine

1.2E-09

7.9E-10

4.2E-10

2.5E-10

1.8E-10

1.6E-10

Upper Large Intestine

9.8E-10

6.7E-10

3.8E-10

2.2E-10

1.5E-10

1.3E-10

Lower Large Intestine

1.3E-09

8.7E-10

4.9E-10

2.8E-10

1.9E-10

1.7E-10

Kidneys

6.1E-09

4.1E-09

2.1E-09

1.3E-09

9.3E-10

1.2E-09

Liver

1.5E-08

1.2E-08

3.7E-09

2.4E-09

1.4E-09

1.7E-09

Muscle

8.2E-10

6.6E-10

3.4E-10

1.9E-10

1.5E-10

1.4E-10

Ovaries

6.1E-10

4.4E-10

2.5E-10

1.4E-10

1.0E-10

8.7E-11

Pancreas

7.0E-10

4.4E-10

2.5E-10

1.5E-10

1.1E-10

9.3E-11

Red Marrow

9.5E-09

8.5E-09

4.2E-09

2.5E-09

2.0E-09

1.8E-09

Spleen

1.3E-09

4.5E-10

2.8E-10

1.8E-09

1.7E-10

1.4E-10

Testes

2.2E-09

7.5E-10

3.9E-10

2.2E-10

1.7E-10

1.5E-10

Thymus

5.9E-10

4.2E-10

2.4E-10

1.3E-10

9.7E-11

8.4E-11

Thyroid

1.5E-09

9.7E-10

5.0E-10

2.9E-10

2.2E-10

2.0E-10

Uterus

6.0E-10

4.3E-10

2.56E-10

1.3E-10

9.9E-11

8.6E-11

Lung

9.1E-10

7.2E-10

3.8E-10

2.1E-10

1.6E-10

1.3E-10

Effectivea

4.0E-08

2.3E-08

1.0E-08

5.9E-09

4.2E-09

3.5E-09

a Sum of weighted equivalent doses (see ICRP 1991).

the age dependence in both the sizes of body organs and the behavior of radon and its decay products in the body. A decrease in the dose per unit intake with increasing age at intake is evident in table 4.5b. The lower consumption of tapwater during childhood results in an intake of dissolved radon during childhood that is a small fraction of the lifetime intake. Thus, despite the higher dose per unit intake at these ages, relative to that of the adult, the lower consumption rates result in intakes in the first 10 years that contribute about 30% to the lifetime risk.

Cancer Risk Per Unit 222RN Concentration in Drinking Water

Estimates of the cancer mortality risk per unit concentration of 222Rn in drinking water were derived with the method of Federal Guidance Report 13 (EPA 1998). That method yields a risk estimate that applies to an average mem-



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